EP2065499B1 - Nozzle bar - Google Patents

Description

The invention relates to a nozzle strip for generating fluid jets in a web consolidation according to the preamble of claim 1.

In the manufacture of nonwoven webs formed by depositing a plurality of fibers, it is known to consolidate the web in a further processing process to increase the integrity of the fibers within a fibrous web. In addition to chemical and thermal consolidation methods, in particular mechanical consolidation methods are used in which the fiber web is penetrated by additional means in order to entangle the fibers together. In particular, fluid jet needling has recently gained importance as a solidification method. In this case, columnar fluid jets are preferably generated under a high pressure of the water, which impinge substantially perpendicular to the fiber web and penetrate it. In this case, the fluid jets in the point of impact lead to the compaction and turbulence of the fibers, so that surface structures form on the fibrous web.

The fluid used is preferably water, which is forced out of nozzle openings under high pressure and impinges with high energy in a radial manner on the fiber web and penetrates this to swirl the fiber. The result of the turbulence is determined essentially by the nature of the water jet and its intensity. For example, it is known that the production of water jets with very high pressures of over 400 bar lead to better results of the strength of the web. However, such high pressures generally have the disadvantage that the signs of wear on the nozzle openings of the so-called nozzle strips increase.

To form the nozzle openings in the nozzle bar, basically two different variants are known in the prior art. In a first variant, the nozzle opening is formed by a nozzle bore in a metal plate, which consists of several bore sections. Such nozzle bores are arranged in the nozzle bar in a row and held on an underside of a nozzle beam. Such a nozzle bar is for example from the WO 2006/063112 A 1 known.

In the known nozzle bar, the nozzle bores are each formed by two merging bore sections. A first bore portion opening into an upper entrance surface forms a cylindrical capillary zone in which the fluid enters under high pressure and concentrates into a fluid jet. In an immediately adjoining second bore section, an expansion zone for widening the fluid jet is provided. The expansion zone extends to an exit surface at the bottom of the nozzle rail. The bore portion of the expansion zone is conically shaped so that an entry diameter at the entry surface widens steadily to an exit diameter at the exit surface. However, such nozzle shapes basically have the disadvantage that if the pressures are too low after the fluid jet has emerged there is the risk of the jet bursting. Such diffuse fluid jets lead to irregularities in the fiber web, which manifests itself for example by a stiffness.

Another known in the prior art variant for forming a nozzle bar is for example from the WO 2005/123616 A2 known. In this known nozzle bar, the nozzle openings are formed by a plurality of components, which are held together sealingly to form a nozzle opening. For example, in an upper plate, a cylindrical nozzle bore containing the capillary zone forms for bundling the fluid jet. In a second immediately adjacent metal plate, a further cylindrical bore is arranged with a larger diameter, which is an expansion zone for expanding the fluid jet. In this case, a diameter step is formed between the capillary zone and the expansion zone, which on the one hand causes turbulence and on the other hand causes pressure losses, which have a reduced impact energy of the fluid jet on the surface of the fibrous web.

Multi-part nozzle openings in nozzle strips are for example also from the DE 100 47 106 A1 and the US 6,668,436 B2 known. In the known nozzle bars inserts are used to produce a nozzle opening in a metal plate. In this case, a plurality of cross-sectional shapes of the nozzle opening are formed between an inlet surface and an outlet surface, but with the disadvantage that at least one diameter step, which causes a cross-sectional enlargement or a cross-sectional constriction, is overcome. US 6,668,436 B2 discloses a generic nozzle bar.

It is an object of the invention to further develop a nozzle bar for the production of fluid jets for a web consolidation of the generic type such that efficient fluid jets with high impact energy can be generated at the lowest possible pressures.

This object is achieved by a nozzle bar with the features of claim 1.

Advantageous developments of the invention are defined by the features and feature combinations of the respective subclaims.

The nozzle bar according to the invention is characterized in particular by the high free-jet quality of the fluid jets. In particular, the good parallelism as well the relatively high impact forces of the fluid jets resulted in the same energy input compared to conventional nozzle strips to a significant increase in nonwoven. The solidification effects that can be achieved by the fluid jets thus make it possible to produce strength structures in fibrous webs with the least possible expenditure of energy. The high free-jet quality of the fluid jets produced also led to a uniform strength of the fiber web in the machine direction and in the transverse direction.

The invention has been solved by the proviso that the production of nozzle bores with more than two continuously merging into each other bore sections in nozzle strips with thin metal plates are not economically feasible. Thus, the nozzle bores in the nozzle bar according to the invention are formed at least from three bore sections, which lead to a continuous change in cross section of the nozzle opening. A first bore section opening into the entry surface forms a capillary zone for bundling the fluid jet. A central bore portion includes the expansion zone for expanding the fluid jet, and a third bore portion opening into the exit surface forms an exit zone for guiding the fluid jet. Thus, it is possible to produce fluid jets emerging in parallel and sharply demarcated from the surroundings, which, when hitting the fiber web over the entire active surface, can convert their impact energy into swirling of the fibers in the fiber web. The result is a high uniformity of the Verwirbelungszonen and thus a high uniformity of the generated solidification in the fiber web.

To stabilize the fluid jets produced, the development of the nozzle bar is preferably used, in which the bore portion of the outlet zone is cylindrical with an outlet diameter at the outlet surface, which outlet diameter in the ratio by a factor of at least 2.5 to a maximum of 5.0 greater than an inlet diameter of the capillary zone at the entrance surface. The ratio of the area between an inlet cross-section and an outlet cross-section makes it possible to essentially determine the conversion of the pressure energy into a kinetic energy. In order to minimize the pressure losses during the generation of the fluid jets on the one hand and to obtain a high kinetic energy on the other hand, the ratio between the outlet diameter and the inlet diameter in the range of 2.5 to max. 5.0 proven to be particularly useful.

Basically, however, there is also the possibility that the bore portion of the exit zone is slightly conical with an opening angle <3 °, wherein an exit diameter at the exit surface is greater than an extension diameter formed at the end of the expansion zone. This makes it possible to use additional nozzle effects in the generation of the fluid jet.

The development of the nozzle strip according to the invention according to claim 4 is particularly advantageous in order to generate a maximum kinetic energy to the fluid jet. For this purpose, the bore portion of the capillary zone is made cylindrical with the inlet diameter at the entry surface and the bore portion of the expansion zone is conical with an opening angle in the range of 8 ° to 15 ° to extend the inlet diameter. This makes it possible to realize very smooth transitions between the bore sections, which avoid the occurrence of turbulent flows.

The bore section of the expansion zone can also be advantageously formed by a plurality of conical regions, wherein the conical regions have different opening angles. For example, the opening angle of the area adjoining the capillary zone could be greater than the opening angle of subsequent areas of the expansion zone.

In order to obtain the lowest possible pressure losses in the bundling of the fluid jets, the bore section of the capillary zone is formed according to an advantageous development of the nozzle bar according to the invention with a length which forms a ratio of l / d in the range of 1 to 1.5 with the inlet diameter.

In contrast, the bore section of the exit zone for guiding the fluid jet has a greater length, so that the length of the exit zone with the length of the capillary zone forms a ratio of> 1.

In principle, the inventive design of the nozzle bar with metal plates executable having a thickness of 1 mm to 5 mm between the entrance surface and the exit surface. However, the best results in the production of water jet and in the production of the nozzle bores has been found particularly in the metal plates with a thickness in the range of 1.5 mm to 3 mm.

Depending on the requirements of the solidification of the fiber web, the nozzle openings can be arranged on the metal plate in a row or in several rows next to each other. Depending on the desired solidification or requirement, the pitches between the nozzle openings in the range of 0.5 mm to 2.5 mm can be performed.

In that regard, the device according to the invention for strengthening a fiber web according to the features of claim 11 is particularly suitable for generating parallel and highly efficient fluid jets for hydrodynamic swirling of fiber webs. For this purpose, the device has a nozzle bar which has at least one nozzle bar according to the invention on a lower side. Such devices for consolidating a fiber web are used with different working widths to solidify a spunbond fiber web.

In order to consolidate such fibrous webs, in the device according to the invention preferably several nozzle bars are used one after the other in the production direction in order to solidify a fibrous web with fluid jets. The fluid is preferably supplied to the nozzle bar at a process pressure of preferably 40 to 200 bar or above.

The nozzle bar according to the invention is explained in more detail below with reference to some embodiments with reference to the accompanying figures.

Fig. 1

schematisch eine Draufsicht auf ein Ausführungsbeispiel einer erfin- dungsgemäßen Düsenleiste

Fig. 2

schematisch ein Ausschnitt einer Querschnittsansicht des Ausführungs- beispiels aus Fig. 1

Fig. 3

schematisch ein Ausschnitt einer Querschnittsansicht eines weiteren Aus- führungsbeispiels einer erfindungsgemäßen Düsenleiste

Fig. 4

schematisch ein Ausschnitt einer Querschnittsansicht eines weiteren Aus- führungsbeispiels der erfindungsgemäßen Düsenleiste

Fig. 5

schematisch eine Ansicht eines Ausführungsbeispiels der erfindungsge- mäßen Vorrichtung

They show:

Fig. 1

schematically a plan view of an embodiment of an inventive nozzle bar

Fig. 2

schematically a section of a cross-sectional view of the exemplary embodiment of Fig. 1

Fig. 3

schematically a section of a cross-sectional view of a further exemplary embodiment of a nozzle bar according to the invention

Fig. 4

schematically a section of a cross-sectional view of another embodiment of the nozzle bar according to the invention

Fig. 5

schematically a view of an embodiment of the inventive device

In the Figures 1 and 2 a first embodiment of a nozzle bar according to the invention is shown in several views. The Fig. 1 shows the embodiment in a plan view and Fig. 2 shows the embodiment schematically in a section of a cross-sectional view. Unless an explicit reference is made to one of the figures, the following description applies to both figures.

The nozzle strip 1 consists of a strip-shaped metal plate 2, which may extend over several meters depending on the working width of the device for solidifying a fiber web. For example, when bonding nonwovens, working widths of several meters are realized. At one end, the metal plate on a fixing opening 4 for handling, which could be used, for example, for fixing to a bottom of a nozzle beam. In the middle region, the metal plate 2 is penetrated by a plurality of nozzle openings 3. The nozzle openings 3 are formed next to one another in a row-shaped arrangement and extend over the length of the working width. In principle, such nozzle openings 3 can also be arranged in several rows.

Each of the nozzle openings 3 is formed by a nozzle bore 5 with a plurality of bore sections 6.1, 6.2 and 6.3. In Fig. 2 is a section of a cross-sectional view with two juxtaposed nozzle bores 5 is shown schematically. The metal plate 2 is bounded by an upper entrance surface 10 and by a lower exit surface 11. The nozzle bore 5 of one of the nozzle openings 3 extends from the entry surface 10 to the exit surface 11. The entry surface 11 opens into a first bore section 6.1. The bore section 6.1 constitutes within the nozzle bore 5 a capillary zone 7, in which a fluid coming from the inlet surface 10 is bundled into a fluid jet. The bore section 6.1 of the capillary zone 7 is cylindrical and forms at the inlet surface 11 the inlet diameter d of the nozzle opening 3.

The first bore section 6.1 is followed by a second bore section 6.2, which is formed in the middle region of the metal plate 2. The bore section 6.2 is embodied within the nozzle bore 5 as an expansion zone 8 for widening the fluid jet. The bore section 6.2 of the expansion zone 8 is for this purpose designed conically with an opening angle α for widening the inlet diameter d. Within the expansion zone 8, a continuous expansion of the flow cross-section determined by the inlet diameter d is thus achieved so that the fluid jet guided in the nozzle bore 5 widens.

The second bore section 6.2 is followed by a third bore section 6.3, which opens into the outlet surface 11 and forms an outlet zone 9 for guiding the fluid jet. The bore section 6.3 of the outlet zone 9 is designed to be cylindrical with an outlet diameter D of the nozzle opening 3 on the outlet surface 11.

In order to be able to generate fluid jets which are as parallel and energy-rich as possible for the nonwoven bonding, in particular the following geometrical conditions have proven to be particularly good. With reference to a thickness of the metal plate, which in Fig. 2 marked with the capital letter S, the first bore section 6.1 extends over a length 1. The length 1 of the capillary zone 7 is preferably greater by a factor of 1 to 1.5 than the inlet diameter cr d. This results in a ratio l / d = 1 to 1.5.

Furthermore, it has been shown that the exit diameter D of the exit zone 9 at the exit face 11 may not be too large in relation to the entry diameter d of the capillary zone 7, since otherwise the fluid jets have too low a kinetic energy. On the other hand, there is a desire to realize the largest possible impact points with the fluid jets on the surface of a fibrous web. Thus, the ratio between the exit diameter D and the entrance diameter d of D / d = 2.5 to 5.0 proved to be particularly effective. In order to obtain a parallelism and exact free radiation formation of the fluid jet, the length L of the exit zone is preferably set larger than the length 1 of the capillary zone. 7

In order to make optimum use of the pressure energy available for generating the kinetic energy, the expansion of the fluid jet in the expansion zone 8 takes place through an opening angle α of 8 ° to 15 °. In principle, larger or smaller opening angles can be realized.

Depending on the requirement of solidification of a fiber web, the nozzle openings 3 with different pitches can be formed side by side in a row arrangement. In order to achieve an intensive turbulence and thus a high strength in a fiber web, narrow pitch distances are preferably realized, which can be up to 0.5 mm depending on the outlet diameter of the nozzle openings. Due to the improved utilization of the pressure energy in the fluid jets still high strengths in a fiber web can be achieved even with larger pitches of up to 2.5 mm. The pitch is in Fig. 2 indicated by the capital letter T, and represents the distance of the centers of the nozzle openings.

Thus, in a comparative experiment with conventional nozzle strips with a nozzle strip according to the invention, which was formed of a metal plate with 2 mm thickness and nozzle openings with an inlet diameter of 0.12 mm, an exit diameter of 0.5 mm and in the region of the expansion zone an opening angle of 13 °, comparable strength values with larger pitches T between the nozzle openings 3 can be realized. Thus, the nozzle bar according to the invention is characterized in particular by the fact that with low Energy input already high solidification results can be realized in a fiber web.

In Fig. 3 a further embodiment of the nozzle bar according to the invention is shown. The nozzle bar is shown as a section of a cross-sectional view. The embodiment according to Fig. 3 is essentially identical to the embodiment according to Fig. 1 and 2 , so that only the differences are explained here.

Compared to the aforementioned embodiment, the central bore section 6.2 of the nozzle bore 5 is divided into a plurality of conical regions. A first conical region 12.1 in this case adjoins directly to the bore section 6.1 of the capillary zone 7. The conical region 12.1 of the bore section 6.2 is formed with an opening angle α ₁ . In the further course of the bore section 6.2, the first conical region 12.1 merges into a second conical region 12.2, which is formed by an opening angle α ₂ . The second conical region 12.2 extends to the end of the bore section 6.2 and continuously merges into the third bore section 6.3 of the exit zone 9.

At the in Fig. 3 illustrated embodiment, the opening angle α _{1 of} the first conical region 12.1 is formed larger than the subsequent conical region 12.2 with the opening angle α _2nd Thus, for example, with such an arrangement, larger opening angles in the range above 15 ° could be realized immediately upon exiting the capillary zone. Thus, the bore section 6.2 in the first conical region 12.1 could have an opening angle of, for example, 24 °, so that in a relatively short inlet of the second bore section 6.2 a larger expansion effect on the fluid jet is produced. The subsequent conical region 12.2 would then preferably receive an opening angle in the range of 8 ° to 15 °.

In Fig. 4 a further embodiment of a nozzle bar according to the invention is shown schematically in a section of a cross-sectional view. The embodiment according to Fig. 4 is also substantially identical to the embodiment of FIG Fig. 1 and 2 , so that only the differences will be explained subsequently and otherwise reference is made to the above description.

At the in Fig. 4 the nozzle orifices 3 are also formed by a nozzle bore 5 with a total of three bore sections 6.1, 6.2 and 6.3. The bore sections 6.1 and 6.2 are identical to the exemplary embodiment according to FIG Fig. 1 and 2 executed.

The exit zone 9 forming third bore section 6.3 of the nozzle bore 5 is not cylindrical in this embodiment. The bore section 6.3 is slightly conical with a small opening angle β. The opening angle β is preferably small in the range <3 °, in order to obtain in particular a sufficient guidance of the fluid jets in the outlet zone 9. In that regard, the exit diameter D formed from the exit surface 11 of the nozzle opening 3 is greater than an extension diameter D _E formed at the end of the second bore section 6.2. The opening angle in the third bore section 6.3 is substantially smaller in relation to the opening angle of the second bore section 6.2 in order to obtain as possible the guidance acting on the fluid jet through the exit zone 9 and to counteract the widening produced by the expansion zone. Again, very sharply demarcated and parallel fluid strands can be generated that only hit genetic energy and thus high impact force on the surface of a fibrous web.

In Fig. 5 an embodiment of the inventive device for solidifying a running fiber web is shown schematically in a view. The exemplary embodiment has a guide means 13 for guiding a fiber web 15. The guide means 13 consists of a screen belt 16, which is preferably formed as an endless belt and is driven by a belt drive 17 at a predetermined belt speed. The screen belt 16 is designed to be air or water permeable. On the surface of the screen belt 16 is formed from a plurality of deposited fibers fiber web 15th

Above the guide means 13 with a small distance to the fiber web 15, a nozzle bar 14 is arranged. The nozzle bar 2 extends substantially transversely across the width of the fiber web 15. The nozzle bar 14 is preferably kept movable and is reciprocated by a drive, not shown here, with a predetermined amplitude. In this case, the nozzle bar 14 moves substantially transversely to the direction of the fiber web 15th

On the underside of the nozzle bar 14, a nozzle bar 1 is held with a plurality of nozzle openings in a row arrangement at a distance from each other. Each of the nozzle openings of the nozzle bar 1 is connected via a pressure chamber, not shown here, with a fluid inlet 19. Via the fluid inlet 19, a fluid is preferably supplied to the nozzle bar 14, a water which is held at a high pressure in a pressure chamber within the nozzle bar 14 and discharged via the nozzle openings of the nozzle bar 1 as a plurality of fluid jets. In Fig. 5 the fluid jets emerging from the nozzle openings on the underside of the nozzle bar 14 are provided with the reference numeral 18.

In operation, the in Fig. 5 shown device continuously penetrated a running fiber web 14 by a plurality of fluid jets. In this case, turbulences and entanglements of the individual fiber strands occur, which improve the cohesion of the fibers and thus lead to an increase in the tensile strength of the fiber web 15.

Due to the efficient fluid jets that can be generated conditionally by the nozzle bar according to the invention, a uniform distribution of the tensile strength both in the longitudinal direction, which is also referred to as machine direction (MD), and in the transverse direction, which is also referred to as CD direction, could be achieved. The device according to the invention is so far particularly suitable for solidifying high-quality fiber webs. Furthermore, energy savings can be realized with the device according to the invention to produce standard strengths in fiber webs.

LIST OF REFERENCE NUMBERS

1

nozzle bar

2

metal plate

3

nozzle opening

4

pegging

5

nozzle bore

6.1, 6.2, 6.3

bore section

7

capillary zone

8th

expansion zone

9

exit zone

10

entry surface

11

exit area

12.1, 12.2

conical area

13

guide means

14

nozzle beam

15

fiber web

16

screen belt

17

capstan

18

fluid jets

19

fluid inlet

Claims (11)

1. Nozzle bar for producing fluid jets in the case of web consolidation, consisting of a metal plate (2) which has, between an upper inlet surface (10) and a lower outlet surface (11), a plurality of nozzle openings (3) arranged next to one another, and having at least one nozzle bore (5) for forming one of the nozzle openings (3), which nozzle bore (5) extends inside the metal plate (2) from the inlet surface (10) to the outlet surface (11) and is formed by a plurality of bore sections (6.1, 6.2) that merge continuously into one another,
   characterized in that
   the nozzle bore (5) has at least three bore sections (6.1, 6.2, 6.3), in that a first bore section (6.1), that opens into the inlet surface (10), forms a capillary zone (7) for concentrating the fluid jet, in that a central bore section (6.2) forms an expansion zone (8) for widening the fluid jet, and in that a third bore section (6.3), that opens into the outlet surface (11), forms an outlet zone (9) for guiding the fluid jet.
2. Nozzle bar according to Claim 1,
   characterized in that
   the bore section (6.3) of the outlet zone (9) has a cylindrical design with an outlet diameter (D) of the nozzle opening (3) at the outlet surface (11), which outlet diameter (D) is proportionally larger than an inlet diameter (d) of the nozzle opening (3) at the inlet surface (10) by a factor of from at least 2.5 to at most 5.0.
3. Nozzle bar according to Claim 1,
   characterized in that
   the bore section (6.3) of the outlet zone (9) has a conical design with an opening angle (β) in the region of < 3°, wherein an outlet diameter (D) of the nozzle opening (3) at the outlet surface (11) is larger than a widening diameter (D_E) formed at the end of the bore section (6.2) of the expansion zone (8).
4. Nozzle bar according to one of Claims 1 to 3,
   characterized in that
   the bore section (6.1) of the capillary zone (7) has a cylindrical configuration with an inlet diameter (d) of the nozzle opening (3) at the inlet surface (10), and in that the bore section (6.2) of the expansion zone (8) has a conical configuration with an opening angle (α) in the region of from 8° to 15° for widening the inlet diameter (d) of the nozzle opening (3).
5. Nozzle bar according to one of Claims 1 to 4,
   characterized in that
   the bore section (6.2) of the expansion zone (8) is formed by a plurality of conical regions (12.1, 12.2), wherein the conical regions (12.1, 12.2) have different opening angles (α₁, α₂).
6. Nozzle bar according to Claim 5,
   characterized in that
   the opening angle (α₁) of the region adjoining the bore section (6.1) of the capillary zone (7) is larger than the opening angle (α₂) of subsequent regions (12.2) of the bore section (6.2) of the expansion zone (8).
7. Nozzle bar according to one of the preceding claims,
   characterized in that
   the bore section (6.1) of the capillary zone (7) has a length (1) which forms with an inlet diameter (d) of the nozzle opening (3) a ratio l/d in the region of from 1 to 1.5.
8. Nozzle bar according to one of Claims 1 to 7,
   characterized in that
   the bore section (6.3) of the outlet zone (9) has a length (L) which forms with the length (1) of the bore section (6.1) of the capillary zone (7) a ratio L/l in the region of >1.
9. Nozzle bar according to one of Claims 1 to 8,
   characterized in that
   the metal plate (2) has a thickness (S) in the region of from 1.5 mm to 3 mm between the inlet surface (10) and the outlet surface (11).
10. Nozzle bar according to one of Claims 1 to 9,
    characterized in that
    the nozzle openings (3) on the metal plate (2) are arranged in a row or a plurality of rows with a separation spacing (T) in the region of from 0.5 mm to 2.5 mm.
11. Apparatus for consolidating a fibre web (15) by means of fluid jets (18) with a nozzle rack (14) which has at least one nozzle bar (1) for producing fluid jets (18) and which is arranged above a moving fibre web (15),
    characterized in that
    the nozzle bar (1) is designed according to one of Claims 1 to 10.

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